优良饲用乳酸菌的筛选及在模拟消化环境中的耐受性

Screening of forage lactic acid bacteria with good tolerance to stimulated animal digestive environments

通过MRS培养基进行初筛,耐酸耐胆盐复筛,从乳猪粪便中筛选出能够应用于饲料中的优良乳酸菌。MRS初筛得到26株乳酸菌疑似菌株,在pH2.0和3 g/L胆盐的MRS培养复筛得到7株菌,对性能较好的菌株G1和G9进行生理生化及分子生物学鉴定：G1为植物乳杆菌（NCU156）、G9为戊糖片球菌（NCU301）。进一步研究NCU156的耐酸耐胆盐性能以及模拟动物消化道耐受性能。结果表明：NCU156在p H2.5的MRS培养基中,作用4 h存活率为87.31%;在胆盐质量浓度为3 g/L的培养基中,作用6 h活菌数下降不到一个数量级;在pH3.0的人工胃液中作用4 h,NCU156的活菌数稍有增加,在3 g/L胆盐的人工肠液中作用6 h,活菌数下降约一个数量级（1.81×10^9-1.27×10^8CFU/m L）,活菌数仍保持在10^8CFU/m L以上。可见NCU156对动物胃肠道有良好的耐受性,在饲料产品中有很好的应用前景。

Twenty six strains were isolated from fresh litter feces using MRS broth. Seven strains with high tolerance to MRS broth（ p H2. 0） and MRS broth with 3g / L bile salt were further screened out. Strains G1 and G9 with better properties were respectively identified as Lactobacillus plantarum and Pedicoccus pentosaceus by morphology,biochemical characteristics and molecular biology identification. Furthermore,the tolerance of NCU156 to acid and bile salt was studied. The animal digestive environments were simulated. The result showed that survival rate of NCU156 was 87. 31% after 4h incubation in MRS（ p H2. 5）. After incubation in MRS with 3 g / L bile salt for 6h,the viable count of NCU156 reduced less than an order of magnitude. The viable count increased slightly after incubation in the artificial gastric fluid with pH3. 0 for 4h. The number of NCU156 reduced about an order of magnitude,but still above10^8 CFU / m L after 6 h in artificial intestinal fluid. L. plantarum NCU156 had excellent tolerance to simulated animal digestive environments and had potential to be used in pellet feed.